[downhole sampling apparatus and method]

Abstract

A method and apparatus for reducing debris in a perforation in a wellbore extending from the wellbore into a subterranean formations is provided. A housing is positioned in the wellbore, and an arm is extended therefrom. One or more plugs are positionable in the perforation via the arm. The plug is adapted to block debris from formation fluid flowing into the housing via the perforation whereby the contamination in the formation fluid is reduced. The plug may be a filter positionable in the perforation, or a bit activated to dislodge debris.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] This invention relates generally to the downhole investigation of subterranean formations. More particularly, this invention relates to sampling through perforations in a wellbore penetrating the subterranean formation. [0003] 2. Background Art [0004] Historically, wells have been drilled to seek out downhole reservoirs containing highly desirable fluids, such as oil, gas or water. The wells may be located on land or over waterbeds and extend downhole into subterranean formations. In the search for oil and gas reserves, new wells are often drilled and tested. The wellbore may remain “open” after drilling, or be provided with a casing (otherwise known as a liner) to form a “cased” wellbore. A cased wellbore is created by inserting a tubular steel casing into an open wellbore and pumping cement downhole to secure the casing in place in the wellbore. The cement is employed on the outside of the casing to hold the casing in...

AI Technical Summary

Benefits of technology

[0019] This apparatus may have some additional features. First, this invention uses perforating means to perforate the casing, preferably capable of creating a more uniform perforation which can be easily plugged and without the need to use of non-solid plugging means. Another advantage is the ability to extend the perforation to lengths in the formation that are greater than the diameter of the borehole. This apparatus may be implemented with a wireline device and does not require tubing, although tubing can be used if desired. Another result of this advantage is more flexibility in aligning a motor and power devices. A further advantage of a form of the present invention is that a perforation can be plugged while the tool is still set in the position at which the perforation was made, so the plugging operation can be specifically and accurately directed to the perforation, without the need for locating the perforation or for wasting the plugging medium by plugging a region that is larger than the perforation itself.

Problems solved by technology

Once the casing is installed, the ability to perform tests is limited by the steel casing.

It is estimated that there are approximately 200 cased wells which are considered for abandonment each year in North America, which adds to the thousands of wells that are already idle.

These abandoned wells have been determined to no longer produce oil and gas in necessary quantities to be economically profitable.

However, the majority of these wells were drilled in the late 1960's and 1970's and logged using techniques that are primitive by today's standards.

While the advances in perforation techniques have assisted in the analysis of open and cased wellbores, it has been discovered that some perforations may become obstructed by debris.

Additionally, debris, such as drilling fluids, mud, dirt and other contaminants, may pollute the sampling or testing process and corrupt the test results.

However, these techniques fail to address the problem of contamination and debris in the perforation.

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